Aldehydes and Ketones Practice Flashcards

A complete set of 250 vocabulary flashcards covering the nomenclature, structure, properties, preparation, and reactions of aldehydes and ketones as described in the lecture notes.

Carbonyl compounds

Organic compounds containing the carbonyl group, such as aldehydes, ketones, carboxylic acids, esters, amides, acid halides, and acid anhydrides.

Carbonyl group

A functional group composed of a carbon atom doubly bonded to an oxygen atom ($C=O$).

Aldehyde

A carbonyl compound with at least one hydrogen atom bonded to the carbonyl carbon atom.

Ketone

A carbonyl compound with two alkyl or aryl groups bonded to the carbonyl carbon atom.

Formyl group

The functional group of an aldehyde ($-CHO$), which consists of a carbonyl group and a hydrogen atom.

Formaldehyde

The simplest aldehyde, containing two hydrogen atoms bonded to the carbonyl group ($HCHO$).

Symmetrical ketone

A ketone in which the two alkyl groups attached to the carbonyl carbon are the same.

Unsymmetrical ketone

A ketone in which the two alkyl groups attached to the carbonyl carbon are different.

Common system naming (Aldehydes)

Names derived from corresponding carboxylic acids by replacing the ending '-ic acid' with '-aldehyde'.

Common name of $HCHO$

Formaldehyde, derived from formic acid.

Common name of $CH_3CHO$

Acetaldehyde, derived from acetic acid.

Common name of $CH_3CH_2CHO$

Propionaldehyde, derived from propionic acid.

Common name of $CH_3CH_2CH_2CHO$

Butyraldehyde, derived from butyric acid.

Common name of aromatic $C_6H_5CHO$

Benzaldehyde.

Greek letters ($\alpha$, $\beta$, $\gamma$)

Used in the common system to indicate the position of substituents relative to the formyl group.

$\alpha$-carbon

The carbon atom immediately adjacent to the carbonyl group.

$\alpha$-methyl butyraldehyde

A naming example where a methyl group is attached to the carbon adjacent to the formyl group in a four-carbon aldehyde.

$\beta$-bromo butyraldehyde

A naming example where a bromine atom is attached to the second carbon from the formyl group.

IUPAC suffix for aldehydes

The ending '-al', which replaces the ending '-e' of the corresponding alkane.

IUPAC prefix for two carbonyl groups

The prefix 'di-' is added before the suffix (e.g., '-dial').

Substituent naming in IUPAC

The rules used are the same as those for alkanes.

Aldehyde ring nomenclature

The suffix 'carbaldehyde' is used if the aldehyde group is attached to a ring.

Stem name identification

Locate the longest chain of carbon atoms containing the formyl group.

Aldehyde carbon numbering

Carbon atoms are numbered starting from the carbon of the formyl group ($-CHO$).

Methanal

The IUPAC name for formaldehyde.

Ethanal

The IUPAC name for acetaldehyde.

Propanal

The IUPAC name for propionaldehyde.

Butanal

The IUPAC name for butyraldehyde.

2-methylpropanal

An isomer of butanal having a methyl group on the second carbon.

4-chloro-3-methylpentanal

A five-carbon aldehyde with a chlorine on carbon 4 and a methyl on carbon 3.

3-methylpent-3-enal

An unsaturated aldehyde with a methyl group and a double bond at carbon 3.

Ethanedial

A two-carbon dialdehyde ($HOC-CHO$).

Propanedial

A three-carbon dialdehyde ($HOC-CH_2-CHO$).

Cyclopentanecarbaldehyde

A five-membered carbon ring with an attached aldehyde group.

Common system naming (Ketones)

Named by writing the names of the alkyl groups followed by the word 'ketone'.

Dimethyl ketone

The common name for acetone.

Ethyl methyl ketone

The common name for butanone.

Diethyl ketone

The common name for pentan-3-one.

Acetophenone

The common name for phenylethanone, an aromatic ketone.

IUPAC suffix for ketones

The ending '-one', which replaces the ending '-e' of the corresponding alkane.

Ketone numbering rule

Number the chain from the end that gives the carbonyl carbon the lowest possible number.

Propanone

The IUPAC name for acetone; no numbering is necessary.

Butanone

The IUPAC name for ethyl methyl ketone; no numbering is necessary.

1-bromobutan-2-one

A four-carbon ketone with a bromine substituent on the first carbon.

Pentan-2-one

A five-carbon ketone with the carbonyl group at the second position.

3-methylbutan-2-one

A four-carbon ketone chain with a methyl group at carbon 3.

Hexane-2,4-dione

A six-carbon chain with two ketone groups at positions 2 and 4.

Cyclohexanone

A cyclic ketone consisting of a six-membered ring.

Aldehyde chain isomerism threshold

Aldehydes containing four or more carbon atoms.

Ketone chain isomerism threshold

Ketones containing five or more carbon atoms.

Position isomerism in ketones

Occurs in ketones with five or more carbon atoms, such as pentan-2-one and pentan-3-one.

Position isomerism in aromatic aldehydes

Occurs in compounds like benzene-1,2-dicarbaldehyde, benzene-1,3-dicarbaldehyde, and benzene-1,4-dicarbaldehyde.

Benzene-1,2-dicarbaldehyde

An aromatic dialdehyde with formyl groups at the 1 and 2 positions.

Benzene-1,3-dicarbaldehyde

An aromatic dialdehyde with formyl groups at the 1 and 3 positions.

Benzene-1,4-dicarbaldehyde

An aromatic dialdehyde with formyl groups at the 1 and 4 positions.

General formula for aldehydes and ketones

$C_nH_{2n}O$.

Functional group isomerism

Isomerism where the same formula belongs to different classes, such as propanal and propanone.

Tautomerism

A type of isomerism shown by aldehydes and ketones involving the shift of a proton and a double bond.

Hybridization of carbonyl carbon

$sp^2$-hybridized.

Hybridization of carbonyl oxygen

$sp^2$-hybridized.

Carbonyl sigma bond ($\sigma$)

Formed by the linear overlap of an $sp^2$ orbital from carbon and an $sp^2$ orbital from oxygen.

Carbonyl pi bond ($\pi$)

Formed by the sidewise overlap of unhybridized p orbitals from carbon and oxygen.

Unshared electron pairs on oxygen

Oxygen in a carbonyl group has two pairs of unshared electrons in its $sp^2$-hybrid orbitals.

Carbonyl geometry

Trigonal planar, with the three attached atoms lying in the same plane.

Carbonyl bond length

$120\,pm$, which is shorter than the $142\,pm$ bond length in alcohols and ethers.

Standard bond angles around carbonyl carbon

Approximately $120^\circ$.

Formaldehyde bond angle (H-C-H)

$116.5^\circ$.

Acetaldehyde bond angle (C-C-O)

$123.9^\circ$.

Acetaldehyde bond angle (C-C-H)

$117.5^\circ$.

Acetone bond angle (C-C-C)

$117.2^\circ$.

Formaldehyde physical state

A gas at room temperature.

Formalin

A 40% aqueous solution of formaldehyde used for storage and as a reagent.

Physical state of most other aldehydes

Colourless volatile liquids.

Ketone physical state

Colourless volatile liquids.

Carbonyl compound polarity

They are polar molecules due to the high dipole moment of the $C=O$ bond.

Boiling point trend (Alkanes vs Carbonyls)

Carbonyl compounds have higher boiling points than alkanes of similar mass due to polarity.

Boiling point trend (Alcohols vs Carbonyls)

Carbonyl compounds have lower boiling points than alcohols because they cannot form hydrogen bonds with themselves.

Boiling point relationship with mass

Boiling points of aldehydes and ketones increase with increasing molecular mass.

Butane boiling point ($bp$)

$0^\circ C$.

Methoxyethane boiling point ($bp$)

$8^\circ C$.

Propanal boiling point ($bp$)

$49^\circ C$.

Acetone boiling point ($bp$)

$56^\circ C$.

Propane-1-ol boiling point ($bp$)

$97^\circ C$.

Solubility threshold

Lower aldehydes and ketones up to four carbon atoms are water soluble.

Solubility trend

Water solubility decreases as the size of the non-polar alkyl group increases.

Reason for water solubility

Formation of hydrogen bonds between the carbonyl oxygen and water molecules.

Hydrogen bonding in carbonyls

They cannot form hydrogen bonds with themselves because there is no hydrogen on the carbonyl oxygen.

Odour of lower aldehydes

Sharp and pungent odour.

Odour of higher aldehydes/ketones

Pleasant odour.

Ozonolysis

The reaction of ozone with alkenes to form an ozonide, which is then reduced to aldehydes and/or ketones.

Ozonide

An unstable intermediate compound formed when ozone reacts with an alkene.

Reduction of ozonide

Performed using Zinc ($Zn$) and water ($H_2O$) at $100^\circ C$.

Symmetrical alkene ozonolysis product

Produces a single product (e.g., trans-but-2-ene yields only acetaldehyde).

Asymmetric alkene ozonolysis product

Produces a mixture of aldehydes and/or ketones.

Ozonolysis of 2-methylbut-2-ene

Produces a mixture of acetaldehyde and acetone.

Hydration of alkynes

Acid-catalyzed addition of water across the triple bond to produce carbonyl compounds.

Alkyne hydration catalysts

Mercuric sulphate ($HgSO_4$) and sulfuric acid ($H_2SO_4$).

Hydration of acetylene product

Acetaldehyde.

Hydration of higher alkynes product

Ketones.

Vinyl alcohol

An unstable intermediate (enol) formed during the hydration of acetylene.